In the welding industry, tremendous numbers of robotic welding stations are operable to draw welding wire from a package as a continuous supply of wire to perform successive welding operations. The advent of this mass use of electric welding wire has created a need for large packages for containing and dispensing large quantities of welding wire. A common package is a drum where looped welding wire is deposited in the drum as a wire stack, or body, of wire having a top surface with an outer cylindrical surface against the drum and an inner cylindrical surface defining a central bore that is coaxial to a central package axis. The central bore is often occupied by a cardboard cylindrical core, as shown in Cooper U.S. Pat. No. 5,819,934, extending about a core axis that is coaxial to the package axis. It is common practice for the drum to have an upper retainer ring that is used in transportation to stabilize the body of welding wire as it settles. This ring, as is shown in Cooper U.S. Pat. No. 5,819,934, remains on the top of the welding wire to push downward by its weight so the wire can be pulled from the body of wire between the core and the ring. In addition, a hold-down mechanism can be utilized to increase the downward force.
The welding wire in the package is in coils or convolutions wrapped about the package axis and the coil has a top and a bottom. The coil further includes radial inner and outer surfaces extending between the top and the bottom of the coil. As the welding wire is removed from the package, the wire is removed from the top coils or convolutions of wire wherein the top of the wire coil moves downwardly into the package. As a result, the top of the wire coil descends within the package and the outer and inner surfaces of the coil become shorter and shorter.
In order to work in connection with the wire feeder of the welder, the welding wire must be dispensed in a non-twisted, non-distorted and non-canted condition which produces a more uniform weld without human attention. It is well known that wire has a tendency to seek a predetermined natural condition which can adversely affect the welding process. Accordingly, the wire must be sufficiently controlled by the interaction between the welding wire package and the wire feeder. To help in this respect, the manufacturers of welding wire produce a wire having natural cast, wherein, if a segment of the wire was laid on the floor, the natural shape of the wire would be essentially a straight line; however, in order to package large quantities of the wire, the wire is coiled into the package which can produce a significant amount of wire distortion and tangling as the wire is dispensed from the package. As a result, it is important to control the payout of the wire from the package in order to reduce twisting, tangling or canting of the welding wire. This condition is worsened with larger welding wire packages which are favored in automated or semi-automated welding.
The payout portion of the welding wire package helps control the outflow of the welding wire from the package without introducing additional distortions in the welding wire to ensure the desired continuous smooth flow of welding wire. Both tangling or breaking of the welding wire can cause significant down time while the damaged wire is removed and the wire is re-fed into the wire feeder. In this respect, when the welding wire is payed out of the welding wire package, it is important that the memory or natural cast of the wire be controlled so that the wire does not tangle. The welding wire package comprises a coil of wire having many layers of wire convolutions laid from the bottom to the top of the package. These convolutions include an inner diameter and an outer diameter wherein the inner diameter is substantially smaller than the width or outer diameter of the welding wire package. The convolutions together form the radial inner and outer surface discussed above. The memory or natural cast of the wire causes a constant force in the convolutions of wire which is directed outwardly such that the diameter of the convolutions is under the influence of force to widen. The walls of the wire welding package prevent such widening. However, when the welding wire payout of the package, the walls of the package lose their influence on the wire and the wire is forced toward its natural cast. This causes the portion of the wire which is being withdrawn from the package to loosen and tend to spring back into the package thereby interfering and possibly becoming tangled with other convolutions of wire. In addition to the natural cast, the wire can have a certain amount of twist which causes the convolutions of welding wire in the coil to spring upwardly.
Payout devices or retainer rings have been utilized to control the spring back and upward springing of the wire along with controlling the payout of the wire This is accomplished by positioning the payout or retainer ring on the top of the coil and forcing it downwardly against the natural springing effect of the welding wire. The downward force is either the result of the weight of the retainer ring or a separate force producing member such as an elastic band connected between the retainer ring and the bottom of the package. Further, the optimal downward force during the shipment of the package is different than the optimal downward force for the payout of the welding wire. Accordingly, while elastic bands or other straps are utilized to maintain the position of the payout or retainer ring during shipping, the weight of the retainer ring can be used to maintain the position of the payout relative to the wire coils during the payout or the wire.
In addition to the braking ring or retainer ring, which helps control the flow of wire from the package, welding wire packages can further include an inner core to help prevent the outgoing wire from looping across the central axis of the package. In this respect, the central core can be positioned in the wire package within the cylindrical inner region defined by the inner surface of the wire coil. The core is coaxial to a core axis in line with the central package axis. The inner core and the outer packaging together form a generally annular coil compartment wherein the wire can only move upwardly, not transversely of the package axis. In general terms, the central core produces an inner barrier for the wire coil to help direct the outgoing wire upwardly and out the top opening of the wire package such that one convolution of wire does not interfere with other convolution of wire.
The welding wire is further controlled by external wire management systems that can include a payout hat that is placed over the top opening of the package and which includes a central opening for the welding wire to pass through. This, alone with other forces and conditions, causes the exiting wire to move toward the central axis of the package as it travels toward this central opening. Further, while the wire is being removed, convolutions of wire are being removed wherein the outgoing wire is constantly moving around the central axis of the package. As a result of the inward movement, the wire tends to engage the inner core is it travels upwardly in the package and as a result of the constant movement about the central axis, this point of engagement with the central core constantly moves around the central core. This produces inward forces on the central core that constantly move about the central core. Further, as the wire moving toward the top opening, it also produces an upward force.
As can be appreciated, when the package is full of wire and the wire coil is nearly the same height of the central core, there is little or no space between the coil and the majority of the central core. This arrangement substantial prevents lateral and/or upward movement of the core relative to the central axis. As a result, the core is relatively stable with a full package. However, as the wire is removed from the package, the coil becomes shorter thereby exposing a greater portion of the top of the core. The lack of support by the inner surface of the coil near the top of the core allows core to move around the package axis at an angle to the package axis. More particularly, lack of support near the top cause the core to tilt about the package axis such the core axis near the top of the core becomes spaced radially outwardly from the package axis while the core axis near the bottom of the core is maintained closer to the package axis, but one side of the core bottom lifts from the bottom of the package. As the top of the wire coil nears the bottom of the package, this condition worsens such that the core axis near the top of the core moves further radially outwardly and the bottom of the core becomes looses even more of its engagement with the bottom such that it becomes unstable until the bottom of the core begins to “walk” up the inner surface of the core. Continued “walking” of the core will eventually cause the bottom of the core to reach the top of the coil. Once the bottom of the coil reaches the top of the coil it is free to move radially outwardly until it interferes with the flow of the outgoing wire and causes a tangle in the outgoing wire. As can be appreciated, a wire tangle will result in the welding operation being shut down until the tangle is removed. If the wire package is nearly empty, the nearly empty wire package may be replaced by a new wire package thereby wasting a significant amount of welding wire.
In order to overcome the shortcomings in cylindrical cores described above, conical central cores have been used to reduce the tendency of the core to tilt and lift as the wire is removed from the package. While the conical core may reduce the tilting and lifting actions of the core, it reduces the effectiveness of the core to help control the removal of the wire from the package. In this respect, a cylindrical core better directs the welding wire to the outlet of the package. Further, the tilting action of the core can have beneficial effects on the outgoing wire if it is controlled and if the bottom of the core is prevented from “walking” up the coil.